Explanation/Reference:
References https://docs.oracle.com/cd/B28359_01/server.111/b28300/expimp.htm#UPGRD12560

A: PGA itself is subdivided. The UGA (User Global Area) contains session state information, including stuff like package-levelvariables, cursor state, etc. Note that, with shared server, the UGA is in the SGA. It has to be, because shared server means that the session state needs to be accessible to all server processes, as any one of them could be assigned a particular session.However, with dedicated server (which likely what you're using), the UGA is allocated in the PGA.
C: The Location of a private SQL area depends on the type of connection established for a session. If a session is connected through a dedicated server, private SQL areas are located in the serverprocess' PGA. However, if a session is connected through a shared server, part of the private SQL area is kept in the SGA.
Note:
* System global area (SGA)
The SGA is a group of shared memory structures, known as SGA components, that contain data and control information for one Oracle Database instance. The SGA is shared by all server and background processes. Examples of data stored in the SGA include cached data blocks and shared SQL areas.
* Program global area(PGA)
A PGA is a memory region that contains data and control information for a server process.
It is nonshared memory created by Oracle Database when a server process is started.
Access to the PGA is exclusive to the server process. There is one PGA foreach server process. Background processes also allocate their own PGAs. The total memory used by all individual PGAs is known as the total instance PGA memory, and the collection of individual PGAs is referred to as the total instance PGA, or just instancePGA. You use database initialization parameters to set the size of the instance PGA, not individual PGAs.
References:

Explanation
Asynchronous Global Index Maintenance for DROP and TRUNCATE PARTITION
This feature enables global index maintenance to be delayed and decoupled from a DROP and TRUNCATE partition without making a global index unusable. Enhancements include faster DROP and TRUNCATE partition operations and the ability to delay index maintenance to off-peak time.
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